Heat exchanger element and method of making the same

ABSTRACT

A heat exchange element employed in heat exchangers of air conditioning system includes a heat exchanging sheet member containing heat meltable synthetic resin fibers and a plurality of elongate rollable shaped spacers. The heat exchanging sheet member has one side on which the spacers are bonded by a heat meltable layer of the synthetic resin fibers contained in the heat exchanging sheet member so that each spacer is spaced from the adjacent spacer on the heat exchanging sheet member. A method of making the heat exchange element includes steps of rolling a plurality of elongate rollable spacers on a base having in an upper face a plurality of spaced grooves so that the spacers are positioned in the respective grooves, unrolling a rolled heat exchanging sheet member containing synthetic resin fibers and placing the unrolled portion of the sheet member over the base, heating an upper side of the sheet member over the base by heaters so that the synthetic resin fibers contained in the sheet member are melted and bonding the spacers to a lower side of the sheet member by a heat melted layer of the synthetic resin fibers, and cutting the sheet member with the spacers bonded to it so as to have predetermined dimensions.

BACKGROUND OF THE INVENTION

This invention relates to a heat exchange element employed in a heatexchanger incorporated in an air conditioning system and a method ofmaking such a heat exchange element.

Conventionally, a so-called corrugated board type heat exchanger hasbeen generally employed in an air conditioning system or the like.Referring to FIGS. 5 and 6, generally rectangular heat exchanging papersheets 1 and corrugated partitions 2 formed, for example, of a specialkraft paper containing calcium chloride are alternately stacked on eachother. The directions of the partitions 2 are alternately changed by 90degrees such that two perpendicular air flow passages 3 are provided.Heat exchange is performed between air flows passing through the airflow passages 3.

In the above-described conventional construction, however, the papersheets 1 and corrugated partitions 2 are alternately stacked on eachother so that each partition 2 is provided over an entire width of eachpaper sheet 1 at an entrance of each air flow passage 3. Furthermore, alarge number of narrow passage portions are formed between thepartitions 2 and the paper sheets 1 in the above-described construction.Consequently, resistance of each air flow passage is increased,resulting large air flow pressure loss.

In order to overcome the above-described disadvantage, the constructionillustrated in FIGS. 7 and 8 has been proposed. Referring to FIGS. 7 and8, a heat exchange element 7 comprises a paper sheet 5 and a pluralityof partition pieces 6 formed from a synthetic resin. The partitionpieces 6 are vertically mounted on one side of the paper sheet 5. Alarge number of such heat exchange elements 7 are stacked so that thedirection of the partition pieces 6 of each heat exchange element 7 arealternately changed by 90 degrees. In this construction, each air flowpassage 8 has a rectangular cross section, which can reduce the air flowpressure loss as compared with the above-described conventionalconstruction. However, producing the above-described heat exchangeelement 7 necessitates a special forming step in which the syntheticresin partition pieces 6 are formed integrally with the paper sheet 5.This special forming step necessitates special production equipment andforming dies, resulting in a considerable increase in the productioncost of the heat exchange element.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a heatexchange element which can be readily produced with the production costincrease restrained and wherein the pressure loss of a fluid flowingthrough flow passages can be reduced and a method of making such a heatexchange element.

The present invention provides a heat exchange element comprising a heatexchanging sheet member containing heat meltable synthetic resin fibersand a plurality of elongate rollable shaped spacers, the heat exchangingsheet member having one side on which the spacers are bonded by a heatmeltable layer of the synthetic resin fibers contained in the heatexchanging sheet member so that each spacer is spaced from the adjacentspacer on the heat exchanging sheet member.

The present invention also provides a method of making a heat exchangeelement, comprising steps of rolling a plurality of elongate rollableshaped spacers on a base having in an upper face a plurality of spacedgrooves so that the spacers are positioned in the respective grooves,unrolling a rolled heat exchanging sheet member containing syntheticresin fibers and placing the unrolled portion of the sheet member overthe base, heating an upper side of the sheet member over the base by aplurality of heaters so that the synthetic resin fibers contained in thesheet member are melted and bonding the spacers to a lower side of thesheet member by a melted layer of the synthetic resin fibers containedin the sheet member, and cutting the sheet member with the spacersbonded thereto so as to have predetermined dimensions.

In accordance with the present invention, air flow passages are formedby providing a plurality of spacers on one side of the heat exchangingsheet member so that the spacers are spaced. Consequently, the pressureloss of the fluid flowing through the passages can be reduced ascompared with the conventional heat exchange element wherein thecorrugated partitions are employed.

Furthermore, since the spacers are bonded to the side of the heatexchanging sheet member, the heat exchange element can be readilyproduced with an cost-effective production equipment.

It is preferable that each spacer be formed from the same kind ofsynthetic resin as composing the synthetic resin fibers contained in theheat exchanging sheet member. Consequently, the spacers can be desirablybonded to the heat exchanging sheet member.

Furthermore, it is preferable that the sheet member be unrolled in thedirection of elongation of the spacers. Consequently, the bending of thesheet member can be straightened by the spacers.

Additionally, it is preferable that each heater include a generallystraight heating face brought into contact with and heating the sheetmember and each heater is set so that the straight heating face thereofintersects the spacers.

Other objects of the present invention will become obvious uponunderstanding of the illustrative embodiment about to be described.Various advantages not referred to herein will occur to one skilled inthe art upon employment of the invention in practice.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiment of the invention will be described with reference to theaccompanying drawings in which:

FIG. 1 is a perspective view of a heat exchange element of oneembodiment in accordance with the invention;

FIG. 2 is a perspective view of the heat exchange elements stacked oneupon another;

FIG. 3 is a schematic perspective view of an apparatus for producing theheat exchange element shown in FIG. 1;

FIG. 4 is a schematic longitudinal side view of the apparatus;

FIG. 5 is a view similar to FIG. 1 showing the construction of aconventional heat exchange element;

FIG. 6 is a view similar to FIG. 2 showing the conventional heatexchange element;

FIG. 7 is a view similar to FIG. 1 showing the construction of anotherconventional heat exchange element; and

FIG. 8 is a view similar to FIG. 2 showing the another conventional heatexchange element.

DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of the present invention will now be described withreference to FIGS. 1 through 4. FIG. 1 illustrates a heat exchangeelement 11 in accordance with the present invention. The heat exchangeelement 11 comprises a generally rectangular heat exchanging sheetmember 12. A plurality of elongate cylindrical or tubular spacers 13 arebonded on one side of the heat exchanging sheet member 12 so as to bespaced on the sheet member. In the embodiment, six such spacers 13 arebonded on the sheet member 12.

The heat exchanging sheet member 12 is formed of a sheet of papercontaining synthetic resin fibers. In the embodiment, the paper contains65 to 70% fibers comprised of polypropylene. This paper is well knownand has recently been used as a paper for Japanese shoji screens orpaper sliding doors used in Japanese houses.

Commercially available polypropylene straws used for sucking beveragesare employed as the spacers 13. The spacers 13 are bonded on the heatexchanging sheet member 12 by a heat meltable layer of the polypropylenefibers contained in the heat exchanging sheet member 12, as will bedescribed in detail later.

A number of the above-described heat exchange elements 11 are stackedone upon another so that the direction of elongation of the spacers 13of each heat exchange element 11 is shifted by 90 degrees, therebyforming a crossflow heat exchanger having two perpendicular air flowpassages 14.

An apparatus for and a method of making the abovedescribed heat exchangeelement 11 will now be described with reference to FIGS. 3 and 4. Theapparatus comprises a base 15 having one end at which it is connected toa stationary member 16 via a shaft 17 for rotatable movement. The base15 has a distal end at which it is moved upwards and downwards by ahydraulic system 18 comprising a hydraulic cylinder. The base 15 has inits upper side six generally V-shaped spaced grooves 19. The spacers 13are to be positioned in the respective grooves 19, as will be describedlater. A hopper 20 is provided over the stationary member 16 foraccommodating a number of spacers 13. A feeder disposed below the hopper20 comprises a solenoid 21 and a guide passage 22. A predeterminednumber of the spacers 20 accommodated in the hopper 20 are fed to thebase 15 side by the feeder 23.

A roll of heat exchanging sheet member 12 is provided at the left handside of the base 15 as viewed in FIG. 3. The heat exchanging sheetmember 12 is drawn out by a drawing apparatus 26 comprising two chucks24 by which a distal end of the heat exchanging sheet member 12 isgrasped and pneumatic or hydraulic cylinder means 25 for moving thechucks grasping the distal end of the heat exchanging sheet member 12.Thus, a predetermined length of the heat exchanging sheet member 12 isdrawn by the drawing apparatus 26. In this regard the heat exchangingsheet 12 is drawn out in the direction of arrow A or in the direction ofelongation of the grooves 19 of the base 15 or the spacers 13.

A plurality of flat plate-shaped heaters 27 are provided over the base15 for vertical movement. Each heater 27 has a lower end straightheating face 27a which is longitudinally perpendicular to the directionof elongation of the grooves 19 or the spacers 13. A cutter 28 isprovided at the right-hand side of the base 15 for cutting the heatexchanging sheet member 12 by a predetermined length, as viewed in FIG.3.

In making the heat exchange element 11 by the above-described apparatus,the heat exchanging sheet member 12 is drawn out by the drawingapparatus 26 and is placed over the base 15. The distal end of the base15 is lowered by the hydraulic system 18 so that the base 15 isinclined. When the spacers 13 are fed to the base 15 side by the feeder23 with the base 15 inclined, the fed spacers 13 roll on the base 15 toget into the respective grooves 19. The distal end of the base 15 israised by the hydraulic system 18 so that the base 15 becomes horizontalwhen the spacers 13 are thus set in the respective grooves 19. Theheaters 27 each heated up to several hundred degrees Celsius are loweredin this condition so that the heating faces 27a are impressed onto theupper side of the heat exchanging sheet member 12 for several seconds.The heat exchanging sheet member 12 is thus heated such that thepolypropylene fibers contained in the sheet are melted by the appliedheat. The spacers 13 are bonded to the lower side of the heat exchangingsheet member 12 by a heat melted layer. In this regard each spacers 13is spot-bonded at the points of intersection with the heating faces 27aof the heaters 27 since each spacer 13 intersects the heaters 27.

Subsequently, the sheet member 12 on which the spacers 13 are bonded iscut by the cutter 28 into pieces with a predetermined length, therebymaking the heat exchange element 11 as shown in FIG. 1.

In accordance with the heat exchange element, a plurality of spacers 13are bonded on one side of the sheet member 1 2 so as t o be s paced fromo ne another. Consequently, the flow resistance of each air flow passagecan be reduced in the above-described heat exchange element as comparedwith the conventional one that includes the corrugated partitions,thereby reducing the pressure loss of the air flow in each air flowpassage 14.

Since the straws are employed as the spacers 13, the interior 13a ofeach straw acts as a air flow passage, resulting in further reduction inthe pressure loss. Furthermore, since each spacer 13 has the weightsmaller than each conventional corrugated partition, the heat exchangeelement 11 and accordingly, the heat exchanger can be light-weighted.Furthermore, each spacer 13 has elasticity. Accordingly, when a numberof the above-described heat exchange elements 11 are stacked one uponanother to form a heat exchanger, the spacers 13 of each heat exchangeelement 11 can be closely contact with the sheet member 12 of theadjacent element 11, thereby preventing air leakage between the spacers13 and the adjacent sheet member 12.

The heat exchange element 11 is formed by bonding a plurality of spacers13 to one side of the sheet member 12. This method of forming theelement 11 does not necessitate expensive forming machine, forming diesand the like which have been required in the conventional method whereinthe synthetic resin partition pieces are formed integrally with thepaper sheet. Thus, the heat exchange element 11 can be readily made withan inexpensive installation.

Each spacer 13 is formed from the same kind of synthetic resin ascomposing the synthetic resin fibers contained in the heat exchangingsheet member 12. Consequently, the spacers 13 can be reliably bonded tothe heat exchanging sheet member 12. Furthermore, since each spacer 13has a circular section allowing it to roll but, at the same time, hasthe elasticity, a sufficient bonding area can be ensured in each spacer13, resulting in further reliability in bonding.

The rolled sheet member 12 is unrolled in the direction of elongation ofthe spacers 13. Consequently, the bending of the sheet member 12 can bestraightened by the spacers 13.

Although the straws have been employed as the spacers 13 in theforegoing embodiment, slender bar-shaped bamboo members with a generallycircular section or so-called bamboo skewers commercially sold in Japanmay be employed for that purpose. In the case of the bamboo skewers,they can be disposed of as a flammable waste since they do not exhalenoxious gas when the heat exchanger is discarded. Furthermore, thesectional configuration of the spacer 13 is not limited to theabove-described one. It may be polygonal even if the spacer 13 isrollable.

The foregoing disclosure and drawings are merely illustrative of theprinciples of the present invention and are not to be interpreted in alimiting sense. The only limitation is to be determined from the scopeof the appended claims.

I claim:
 1. A heat exchange element comprising a heat exchanging sheetmember containing heat meltable synthetic resin fibers and a pluralityof elongate rollable shaped spacers, the heat exchanging sheet memberhaving one side on which the spacers are bonded by a heat meltable layerof the synthetic resin fibers contained in the heat exchanging sheetmember so that each spacer is spaced from the adjacent spacer on theheat exchanging sheet member.
 2. A heat exchange element according toclaim 1, wherein each spacer is formed from the same kind of syntheticresin as composing the synthetic resin fibers contained in the heatexchanging sheet member.